Add the lines added to the Adjustment type

## Problem
Currently the Adjustment type only tracks the overall delta in lines. This means that if the delta is negative, it is possible to fail to attribute some trailing macro generated code correctly.

## Proposed solution

The Adjustment type should also keep track of the number of lines it added. This should be used to determine if expanded source code originates from a macro or not.

Start by locating the Rust Adjustment type and the code that uses its overall line delta during macro expansion. Trace how expanded Solidity source is attributed, then verify that negative deltas and trailing macro-generated code are handled using the added-line count.

Written by the indexing model from the issue text.